Plastic co-extrusion apparatus with selectable polymer flow control and product produced using the apparatus

ABSTRACT

Co-extrusion apparatus for manufacturing a laminated plastic film or sheet comprises a plug-type layer sequencer including a plurality of channels for conducting a plurality of polymer flows; a transitional aspect ratio block for inducing the plurality of polymer flows to converge; and a flow velocity profiler cartridge for combining the plurality of polymer flows to form the film. In accordance with one embodiment, the layer sequencer includes a tapered selector pin which minimizes mechanical damage when the selector pin is removed. In accordance with another embodiment, the flow velocity profiler cartridge includes inserts fitting within cavities for controlling the polymer flows which form the layers of the film or sheet manufactured by the apparatus. At least one such insert defines lanes within an associated cavity so as to promote the formation of lanes of differing polymer composition within at least one layer of the laminated sheet or film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/919,021, filed Aug. 16, 2004, which is a continuation ofInternational Application No. PCT/US03/05123 having an internationalfiling date of Feb. 20, 2003, which designated the United States, andwhich in turn claims the benefit under 35 USC §119(e) of U.S.Provisional Patent Application Ser. No. 60/358,974, filed Feb. 22, 2002,the entireties of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to the field of apparatus for co-extrudinglaminated polymer films or sheets, and more particularly to co-extrusionapparatus adapted to selectively deliver polymer from a plurality ofextruders to reconfigurable, substantially parallel, converging channelsso as to form laminated plastic films or sheets.

Plug-type flow diverters or layer sequencers have been employed in theco-extrusion of laminated plastic films and sheets. Known plug-typelayer sequencers, such as those taught in Cloeren U.S. Pat. No.4,839,131 and Cloeren et al. U.S. Pat. No. 4,784,815, comprise housingsand cylindrical selector plugs or pins which cooperate to direct resinor fluent polymer from a plurality of extruders into sequences ofpolymer flows which can be recombined to form the films or sheets. Oneadvantage to the use of plug-type layer sequencers is adaptability: asingle layer sequencer may be used to produce a number of differentsequences of polymer flows and, hence, a number of different laminatedstructures, merely by substituting selector pins having differentarrangements of channels for distributing the polymer flows. Anotheradvantage is that the selector pins can be removed for cleaning. Onceinstalled, however, a selector pin must form a tight seal with thehousing so as to confine the polymer flows, which can reach pressures ashigh as 4.5 kpsi and temperatures as high as 640° F. (˜338° C.), in thechannels.

One drawback to known plug-type layer sequencers is the difficulty ofremoving the selector pin for cleaning or substitution without causinggalling or other mechanical damage to the associated surfaces of theselector pin and the housing. In order to minimize such damage, theclearances between the associated surfaces of the selector pins and thehousings of known layer sequencers are generally around 0.008 inch to0.012 inch (˜0.2 mm to ˜0.3 mm). Such clearances are larger thandesirable for forming metal-to-metal mechanical seals. As a consequence,it is possible for some polymer to flow into the spaces between theselector pins and the sockets, and for the polymer flowing into thesespaces to degrade or char, making the removal of the selector pinsdifficult. There remains a need in the art for co-extrusion apparatusincluding plug-type layer sequencers having readily demountable selectorpins nonetheless capable of forming tight mechanical seals withassociated housings.

In conventional co-extrusion apparatus, differences in rheology and flowgeometry between adjacent polymer flows can produce shear forces andother disuniformities between the adjacent flows, resulting indistortion of the layers of a film or sheet produced by the apparatus.Although these shear stresses can be reduced to a greater or lesserdegree by placing the layer sequencers of the assemblies close to thecombining blocks in which the polymer flows are combined to form thefilms or sheets, other engineering considerations often requiresubstantial spacings between the layer sequencers and the combiningblocks.

A further drawback of prior art designs resides in a difficulty ofmaintaining very thin skin layers. Layer uniformity with poor accuracylimits the ability to extrude thin layers of polymers with improvedproperties that can yield significant cost savings. Further difficultieswith many conventional combining blocks include complexity, relativelyhigh expense and lack of an ability to provide individual select flowpaths and geometries without changing out and replacing the entireblocks.

For some applications, it would be desirable to produce laminatedplastic films or sheets having layers or strata includingsharply-defined lanes of differing polymer composition. There remains aneed in the art for co-extrusion apparatus capable of producing films orsheets having such lanes.

SUMMARY OF THE INVENTION

These needs and others are addressed by apparatus in accordance with thepresent invention. In accordance with a first embodiment of theinvention, a preferred co-extrusion apparatus comprises a layersequencer for conducting a plurality of polymer flows; a transitionalaspect ratio block for inducing the polymer flows to converge; and acombining block for combining the polymer flows to produce a film orsheet. The preferred layer sequencer includes a housing and a selectorpin which cooperates with the housing to define a plurality of channelsfor conducting the polymer flows through the layer sequencer. Thehousing defines a socket. The socket defines an opening and a socketprofile tapering inwardly from the opening. The selector pin defines atapering selector pin profile matched to the socket profile so as toenable a seal to form between the selector pin and the socket.

The inward taper of the preferred selector pin and socket permits theeasy removal of the selector pin from the socket. Since the selector pinis tapered, a small outward movement of the selector pin relative to thesocket tends to release the engagement between the two elements. Thisallows the selector pin to be removed without significant galling orother mechanical damage, even when the clearance between the selectorpin and the socket is sufficiently tight to form a metal-to-metalmechanical seal. Furthermore, since the selector pin and socket aretapered, it is difficult to insert the selector pin in the wrong way.

Thus, the configurations of the preferred selector pins and socketspromote the use of clearances sufficiently close to allow the formationof relatively tight mechanical seals between the selector pins and thesockets. The mechanical seals thus formed are capable of withstandingrelatively high internal pressures so as to significantly reduce thelikelihood of cross-contamination of the polymer flows. It is thereforepossible to use relatively thin, closely-spaced channels for conductingpolymer flows through the layer sequencer. This has the beneficialeffects of increasing the number of layers which may be co-extruded bythe apparatus; reducing the size of the preferred selector pin for agiven number of layers; and reducing the polymer inventory within thechannels. The likelihood of cross-channel contamination of even highpressure polymer flows is reduced due to the tightness of the seal.

A second embodiment of the invention is preferably designed tomanufacture plastic films or sheets having layers comprising lanes orstripes of differing polymer composition. In this manner, the preferredembodiment is capable of producing films or sheets having coloredstripes or non-isotropic physical properties. More specifically, throughthe selection of plastics having appropriate physical properties, theapparatus might produce films or sheets having controlled lanes of highstrength or low strength; controlled tear strips; controlled heat seallanes; or controlled adhesive lanes for packaging applications. Suchfilms or sheets might include controlled lanes of high strengthmaterials along cut lines to diminish the likelihood of tear-outs andreduced material stretch caused by slitting. Similarly, the costs offilms or sheets bearing functional coatings could be reduced by limitingsuch coatings to discrete lanes so as to exclude coverage of areas ofthe film which do not require such coatings. The preferred embodimentmight also produce films or sheets having controlled lanes of low andhigh adhesion polymers co-extruded on a homogenous substrate layer so asto allow intermittent cross-web adhesion between layers of the film orsheet. Alternatively, adjacent lanes of differently-colored plasticcould be feathered so as to control the sharpness of the edges or weldlines between the different colors.

Likewise, the second embodiment of the invention is capable ofmanufacturing plastics films or sheets adapted for particularapplications. For example, films having controlled functional lanes offiller, metallic or conductive polymer might be used in the receptorsfor microwavable bags. Likewise, one might co-extrude lanes of acrylicresin to form fiber-optic ribbon cable or lanes of hydroscopic resin toact as water conduits for cooling and filtration purposes. Each of theadaptations mentioned hereinabove exploits the capacity of the preferredembodiment of the invention to conveniently form sharply-defined lanesof differing composition within the layers of co-extruded sheet or filmand to conveniently control the sizes and compositions of those layers.

In accordance with the second embodiment, preferred co-extrusionapparatus comprises a layer sequencer including a plurality of channelsfor conducting a plurality of polymer flows; a transitional aspect ratioblock for inducing the polymer flows to converge; and a flow velocityprofiler cartridge for combining the polymer flows to form the film. Anexample of a flow velocity profiler cartridge is shown and described inInternational Application PCT/US00/34567, filed Dec. 20, 2000, thedisclosure of which is incorporated by reference. The flow velocityprofiler cartridge defines a plurality of cavities for receiving aplurality of inserts. At least one of the inserts includes a pair ofparallel rails spaced along a width direction, a web extending betweenthe pair of parallel rails and at least two indentations on said web forforming at least two passageways. Most preferably, the flow velocityprofiler cartridge defines at least two inlets in communication witheach cavity in receipt of such insert or inserts so that at least one ofthe inlets communicates with each passageway to conduct parallel lanesof polymer through each such cavity for combination into layers of thefilm or sheet manufactured by the co-extrusion apparatus.

The preferred co-extrusion apparatus promotes the formation of plasticfilms or sheets having layers possessing high degrees of uniformity,including layers having lanes with sharply defined edges. The spacesbetween the inserts and the walls surrounding the cavities definepassageways which conduct the polymer flows through the flow velocityprofiler cartridge. By substituting inserts of varying shapes andthicknesses, one varies the geometries of the passageways. Thisvariation of the flow geometries provides control over the flowvelocities and pressure drops within the polymer flows. Matching theflow velocities and shear rates of adjacent flows serves to improve theuniformity of the film or sheet produced by the co-extrusion apparatus,even in cases where the layer sequencer is spaced from the flow velocityprofiler cartridge. The preferred flow velocity profiler cartridge iscapable of accommodating plates or other structure for controlling theeffects of non-linear flow anomalies.

Furthermore, the preferred co-extrusion apparatus promotes the formationof films or sheets having relatively thin polymer layers, since thedimensions of each layer can be controlled by means of inserts shapedspecifically for the polymer component and layer thickness desired. Thepreferred flow velocity profiler cartridge adapts simply andinexpensively to the manufacture of different film or sheet structures:where it is desired to change the structure of the film or sheet to bemanufactured by the co-extrusion apparatus, one merely replaces one ormore inserts rather than the entire combining block. It is possible tostack the preferred flow velocity profiler cartridges so as to generatea number of thin layers to improve barrier properties of common resins.

In addition, the preferred co-extrusion apparatus promotes themanufacture of laminated films or sheets having layers possessingparallel lanes of differing composition. It is possible to form layershaving different lane arrangements within the same laminated film orsheet merely by placing inserts having different arrangements ofpassageways in different cavities of the flow velocity profilercartridge.

Most preferably, the passageways through which pass the polymer flowsdefining the lanes lie adjacent to one another so as to promote theformation of sharply-defined edges and to minimize the likelihood thatpolymer will degrade or become contaminated in the flow velocityprofiler cartridge. The edge or weld lines between adjacent layers formas the polymer flows exit the passageways. Control of the geometries ofthe passageways so as to match the velocities and shear rates ofadjacent polymer flows promotes the formation of sharply-defined edgesbetween the polymer lanes. Since the preferred passageways lie adjacentto one another, there is no dead space upstream of the passageways topermit either mixture or contamination of adjacent flows. By varying theprofile of the joining of the polymer edges it is possible to vary thecolor intensity or barrier properties throughout the region.

The preferred structure provides significant flexibility in thearrangement of the lanes within a layer. The arrangement of the lanesneed not be symmetrical about a centerline of the sheet.

Therefore, it is one object of the invention to provide a co-extrusionapparatus having a plug-type layer sequencer with a tapered selector pinwhich minimizes mechanical damage when the selector pin is removed andreplaced. It is another object of the invention to provide co-extrusionapparatus having a flow velocity profiler cartridge including insertsfitting within cavities for controlling the polymer flows which form thelayers of the film or sheet manufactured by the apparatus, in which atleast one insert defines lanes within an associated cavity so as topromote the formation of at least one inhomogeneous layer. Other objectsand advantages of the invention will be apparent from the foregoing andfollowing descriptions, and the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially-sectioned front elevational view of a co-extrusionapparatus in accordance with the invention, with paths of discretepolymer flow segments or layers through the assembly shownschematically;

FIG. 2 is a side elevational view of a plug-type layer sequencer or flowdiverter for use in the co-extrusion apparatus of FIG. 1;

FIG. 3 is a sectional view of the plug-type layer sequencer of FIG. 2,taken along the line 3-3 in FIG. 2;

FIG. 4 is a bottom plane view of a flow velocity profiler cartridge foruse in the co-extrusion apparatus of FIG. 1;

FIG. 5 is a top plan view of the flow velocity profiler cartridge ofFIG. 4;

FIG. 6 is a schematic sectional view of the flow velocity profilercartridge of FIG. 4, taken along the line VI-VI in FIG. 5;

FIG. 7 is a side elevational view of a first embodiment of an insert foruse in the flow velocity profiler cartridge of FIG. 4;

FIG. 8 is a sectional view of the insert of FIG. 7, taken along the lineVIII-VIII in FIG. 7;

FIG. 9 is a side elevational view of a second embodiment of an insertfor use in the flow velocity profiler cartridge of FIG. 4;

FIG. 10 is a first sectional view of the insert of FIG. 9, taken alongthe line X-X in FIG. 9;

FIG. 11 is a second sectional view of the insert of FIG. 9, taken alongthe line XI-XI in FIG. 9; and

FIG. 12 is a schematic sectional view of a laminated plastic film orsheet of a type manufacturable by the co-extrusion apparatus of FIGS.1-11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, preferred co-extrusion apparatus 10 comprises aplug-type flow diverter or layer sequencer 20; an intermediate heightadjustment block 22; a transitional aspect ratio block 24; and anextruder die 26 defining an outlet 28 and a recess 30 communicating withthe outlet 28. Most preferably, a demountable flow velocity profilercartridge or combining block 32 is positioned in the recess 30. In use,resin or fluent polymer from a plurality of extruders (not shown) entersthe layer sequencer 20. The resin or fluent polymer is directed throughthe layer sequencer 20 so as to form a sequence of polymer flows alongpaths 40. (Although provision for fourteen polymer flows is suggested inFIG. 1, the number of such flows is not critical to the invention.)These polymer flow paths 40 extend through the intermediate heightadjustment block 22 and converge toward one another in the transitionalaspect ratio block 24. The polymer flow paths 40 further converge andnarrow in the flow velocity profiler cartridge 32, ultimately forming alaminated film or sheet which exits the extruder die 26 through theoutlet 28.

As shown in FIGS. 2 and 3, a preferred layer sequencer 20 comprises ahousing 50 and a selector pin or plug 52. As best shown in FIG. 3, thepreferred layer sequencer 20 defines three recessed inlets 60, 62 and 64for receiving resin or fluent polymer from three different extruders(not shown). (Inlets 62 and 64 exit through the rear or hidden surfaceof the housing 50). The housing 50 also defines five outlets 70, 72, 74,76 and 78. A plurality of channels 80, 82 and 84 communicate between theinlets 60, 62, 64 and the outlets 70, 72, 74, 76, 78.

Preferably, the housing 50 further defines an inwardly tapered socket 90for receiving the selector pin 52. More specifically, the preferredsocket 90 is frustoconical in shape, forming an opening 92 through onesurface of the housing. The preferred selector pin 52 defines aninwardly tapering body portion 100 for receipt in the socket 90 and ahead portion 102 which abuts the housing 50 when the selector pin 52 isreceived in the socket 90. It is desirable that the selector pin 52 beeasily removable from the socket 90 for cleaning.

The preferred socket 90 and the preferred body portion 100 are inwardlytapered in the sense that they each define a maximum cross-section nearthe opening 92 and a minimum cross-section opposite the opening 92. Mostpreferably, the body portion 100 of the selector pin 52 is alsofrustoconical.

The preferred body portion 100 defines a plurality of connecting channelsections 112, 114 and 116 which selectively communicate between theinlets 60, 62, 64 and the outlets 70, 72, 74, 76, 78. Most preferably,each outlet 70, 72, 74, 76, 78 communicates with only one of the inlets60, 62, 64.

While it is desirable that the selector pin 52 be easily removable fromthe socket 90 for cleaning, a relatively tight seal must be formed whenthe selector pin 52 is inserted in the socket 90 of the housing 50 sothat the resin or fluent polymer in the channels 80, 82, 84 movesdirectly from the inlets 60, 62, 64 to the outlets 70, 72, 74, 76, 78and does not accumulate in the space between the socket 90 and theselector pin 52. To this end, the profile of the body portion 100 of thepreferred selector pin 52 is matched to the profile of the socket 90 soas to enable a mechanical seal to form between the body portion 100 ofthe selector pin 52 and the socket 90. Most preferably, the body portion100 of the selector pin 52 has a frustoconical profile matched to asimilar profile of the preferred socket.

The inward tapers of the preferred socket 90 and of the preferred bodyportion 100 of the preferred selector pin 52 promote the easy removal ofthe selector pin 52 from the socket 90. Since the selector pin 52 istapered, a small outward movement of the selector pin 52 relative to thesocket 90 tends to release the mechanical seal between the selector pin52 and the socket 90, allowing the selector pin 52 to be removed withoutsignificant galling or other mechanical damage which would impede theformation of a mechanical seal when that selector pin 52, or anotherselector pin (not shown), is replaced in the socket 90.

The inward taper of the preferred body portion 90 is finite but small topromote the formation of a tight mechanical seal. Thus, for example, ifthe body defines a maximum cross-sectional diameter 120 near the opening92; a minimum cross-sectional diameter 122 opposite the opening 92; anda distance 124 along the extension between the maximum and minimumcross-sections, the ratio of the difference between the maximum andminimum diameters 120, 122, on the one hand, and the length 124 of theextension between the maximum and minimum cross-sections, on the other,may be finite but on the order of 5% or less. The ratio in theconfiguration shown in FIG. 3 is between approximately 3% and 4%. The 5%ratio itself is not critical but rather is suggestive of measuresproviding an especially preferred balance between ease of removal andtightness of seal.

The housing 50 and the selector pin 52 are preferably each formed of ametallic material. Most preferably, a heat source (not shown) heats thehousing 50 so as to control the temperature in the channels 80, 82, 84to maintain the fluency of the resin or fluent polymer flowing throughthe layer sequencer 20 toward the transitional aspect ratio block 24 andthe flow velocity profiler cartridge 32.

As shown in FIGS. 4-6, a preferred flow velocity profiler cartridge 32for use in the assembly of FIG. 1 includes a cartridge body 130surrounded by a pair of side caps 132 and 134. Most preferably, thecartridge body 130 and the side caps 132, 134 are formed from a metallicmaterial and the side caps 132, 134 are demountably coupled to thecartridge body 130 by means of bolts so as to permit access to the sidesof the cartridge body 130. As best shown in FIG. 4, the cartridge body130 defines a cartridge outlet 136 at a narrow, lower end thereofthrough which the polymer which flows through the flow velocity profilercartridge 32 can exit into the outlet 28 of the extruder die 26. (Thedesignation “lower,” used to describe the narrow end of the cartridgebody 130, is not intended as a limitation on the orientation of thecartridge body 130, but rather reflects the particular orientation shownin the preferred assembly as depicted in FIG. 1.) As best shown in FIG.5, the cartridge body 130 also defines a sequence of parallel, slot-typeinlets 140 at a broad, upper end thereof. The number of slot-type inlets140 shown in FIG. 5 corresponds to the number of polymer flow paths 40shown schematically in FIG. 1, but this number is not critical to thepresent invention.

As best shown in FIG. 6, pairs of the slot-type inlets 140 communicatewith the cartridge outlet 136 through a sequence of elongated,converging cavities 150 separated by a plurality of tapering partitions152. The cavities 150 extend entirely through the cartridge body 130 ina direction normal to the cutting plane of FIG. 6 (that is, normal tothe line 6-6 in FIG. 5). The cross-sections of the cavities 150 narrowin the direction approaching the cartridge outlet 136. The partitions152 extend from the upper end of the cartridge body 130 to a levelspaced from the cartridge outlet 136 so as to define a combining zone154 communicating between the cavities 150 and the cartridge outlet 136.One or more recesses 156, 158 are optionally formed in the cartridgebody 130 for receipt of heating elements, preferably rod-type electricheating elements, which serve to maintain the fluency of the resin orfluent polymer within the flow velocity profiler cartridge 32 (FIGS. 1,4 and 5).

Inserts 162 and 164 (only two numbered) inserted into the cavities 150serve to control the velocities and shear rates of polymer flows (notshown) through the flow velocity profiler cartridge 32 (FIGS. 1, 4 and5). Thus, in practice, the polymer flows (not shown) enter the cartridgebody 130 through the slot-type openings 140 (FIG. 5); flow through thecavities 150 in the spaces between the inserts 162, 164 and thepartitions 152; and combine in the combining zone 154 to form thedesired film or sheet (not shown).

As shown in FIG. 7, a first preferred insert 162 includes a pair ofparallel rails 170 and 172 spaced along a width direction 174 and acontinuous, impermeable web 176 extending between the rails 170, 172. Asbest shown in FIG. 8, the insert 162 defines a pair of indentations 180and 182 on opposite sides of the web 176. When the insert 162 isinserted into one of the cavities 150 (FIG. 6), the indentations 180,182 cooperate with the adjacent walls 152 (FIG. 6) of the associatedcavity 150 to form a pair of passageways communicating between theassociated slot-type opening 140 (FIG. 6) and the combining zone 154(FIG. 6). By precisely controlling the depths of the indentations 180,182, and, thus, the thicknesses of the passageways defined by theindentations 180, 182, it is possible to match the flow velocities andshear rates of adjacent polymer flows (not shown), so as to minimize thelikelihood of disuniformities between adjacent layers of the finishedfilm or sheet (not shown).

As shown in FIG. 9, a second preferred insert 164 includes a pair ofrails 190 and 192 spaced along a width direction 194 and a continuous,impermeable web 196 extending between the rails 190, 192. Unlike the web176 (FIGS. 7 and 8) of the first preferred insert 162 (FIGS. 7 and 8),however, the web 196 is divided into a plurality of segments 200, 202,204, 206 and 208. The segments 200, 202, 204, 206, 208 definealternately-facing indentations 210, 212, 214, 216 and 218. When theinsert 164 is inserted into one of the cavities 150 (FIG. 6), theindentations 210, 212, 214, 216, 218 cooperate with the adjacent walls152 (FIG. 6) of the associated cavity 150 to form parallel passagewayscommunicating between the associated slot-type openings 140 (FIG. 6) andthe combining zone 154 (FIG. 6) so as to create parallel lanes within alayer of a film or sheet manufactured by the apparatus 10 (FIG. 1).

As shown in FIGS. 10 and 11, the oppositely-facing segments 202, 204preferably have rectangular cross-sections and are similar in profile,with due differences in the depths of the indentations 212, 214 forpurposes of matching the velocities and shear rates of the polymer flows(not shown) past these segments 202, 204. In the embodiment shown inFIGS. 10 and 11, the indentations 212, 214 diverge more strongly in theregion near the combining zone 154 (FIG. 6) than in the region near theslot-type inlets 140 (FIG. 6) so as to regulate the polymer flowsthrough the passageways defined by the indentations 210, 212, 214, 216,218 (FIG. 9). Control of the geometries of the passageways defined bythe indentations 210, 212, 214, 216, 218 (FIG. 9) so as to match thevelocities and shear rates of adjacent polymer flows promotes theformation of sharply-defined edges between the polymer lanes. Thoseskilled in the art will appreciate, however, that (1) the number ofsegments 200, 202, 204, 206, 208 shown in FIG. 9, (2) the arrangement ofthose segments as shown in FIG. 9, and (3) the specific profiles of theindentations 212, 214 shown in FIGS. 10 and 11 are not critical to thepresent invention.

Most preferably, the indentations 210, 212, 214, 216, 218 (FIG. 9)define inwardly sloping or converging surfaces 220 and 226 (only oneeach labeled in FIGS. 10 and 11) terminating in vertices 222, 224 and228 (only three labeled in FIGS. 10 and 11) facing the inlets 140 (FIG.9). These vertices 222, 224, 228 serve to direct the polymer flows (notshown) into the passageways defined by the indentations 210, 212, 214,216, 218 (FIG. 9), thereby impeding the accumulation and possiblemixture of the polymer flows.

Most preferably, the preferred insert 162 or 164 (FIG. 6) is removablyreceived within the cartridge body 130 (FIG. 6) by removing one or bothof the side caps 132, 134 (FIGS. 4 and 5) and sliding the insert 162,164 transversely of the length of the respective cavity 150 (FIG. 6).The side caps 132, 134 (FIGS. 4 and 5) serve to secure the inserts 162,164 (FIG. 6) in the cavities 150 (FIG. 6) and to confine the polymerflows (not shown) through the velocity profiler cartridge 32 (FIGS. 1, 4and 5) to those cavities 150. The lengths of the preferred inserts 162,164 (FIG. 6) correspond to the full length of the cartridge body 130(FIG. 6) so that the outer surface of the preferred inserts 162, 164 areco-planar with adjacent enclosing surfaces of the side caps 132, 134(FIGS. 4 and 5) so as to form polymer-tight seals.

FIG. 12 is a schematic sectional view of a laminated plastic film 230 inaccordance with the invention. The laminated film 230 comprises aplurality of layers, including a first layer 232; a second layer havinglanes 234 and 236; a third layer 238; and a fourth layer 240. Mostpreferably, the lanes 234 and 236 comprise different polymercompositions, such as, for example, compositions of different colors ordifferent physical properties. In accordance with one possibleembodiment, the lane 236 might comprise polymer containing pigment orother coloring agent for displaying a first color, while the lane 234might comprise colorless transparent or translucent polymer or,alternatively, polymer containing pigment or other coloring agent fordisplaying a second color. Those skilled in the art will appreciate thatthe structure of the film 230 shown in FIG. 12 is exemplary only andthat many other structures are within the contemplation of theinvention.

Thus, the preferred embodiment provides a plug-type layer sequencer 20(FIGS. 2 and 3) having an inwardly tapered selector pin 52 (FIGS. 2 and3), such that a small outward movement of the selector pin 52 relativeto a socket 90 (FIG. 3) tends to release a mechanical seal between theselector pin 52 and the socket 90, allowing the selector pin 52 to beremoved without significant galling or other mechanical damage whichwould impede the formation of a mechanical seal when that selector pin52, or another selector pin (not shown), is replaced in the socket 90.In addition, the preferred embodiment provides a flow velocity profilercartridge 32 (FIGS. 4-6) including one or more inserts 164 (FIGS. 9-11)which serve to promote the formation of lanes 234, 236 (FIG. 12) havingsharply-defined edges within the layers of a co-extruded film or sheetwhile minimizing the likelihood that polymer will degrade or becomecontaminated in the flow velocity profiler cartridge 32. Indeed, thepreferred layer sequencer 20 (FIGS. 2 and 3) and the preferred flowvelocity profiler cartridge 32 (FIGS. 4-6) cooperate in that thepreferred layer sequencer 20 simplifies the distribution of the sequenceof polymer flows to the inlets 140 (FIGS. 5 and 6) of the preferred flowvelocity profiler cartridge 32 while the preferred flow velocityprofiler cartridge 32 serves to combine that sequence of polymer flowsinto the desired laminate structure.

1. A co-extrusion apparatus comprising a layer sequencer, a transitionalaspect ratio block, and a combining block, said layer sequencercomprising a housing and a selector pin which cooperates with saidhousing to define a plurality of channels; said transitional aspectratio block comprising a plurality of passages which communicate withsaid channels and which converge; said combining block comprising aplurality of cavities which communicate with said passages and whichconverge; said housing defining a socket for receiving said selectorpin, said socket having an opening and a socket profile taperinginwardly from said opening; and said selector pin defining a taperingselector pin profile substantially matched to said socket profile.
 2. Aco-extrusion apparatus as recited in claim 1, wherein said housingdefines a plurality of inlets and a plurality of outlets, said pluralityof channels providing communication between said plurality of inlets andsaid plurality of outlets.
 3. A co-extrusion apparatus as recited inclaim 1, wherein: said housing defines a plurality of inlets and saidplurality of outlets, and said selector pin defines connecting channelsections of said channels for selective communication between saidplurality of inlets and said plurality of outlets.
 4. A co-extrusionapparatus as recited in claim 1, wherein at least a portion of saidselector pin is frustoconical.
 5. A co-extrusion apparatus as recited inclaim 1, wherein said combining block comprises a removable flowvelocity profiler cartridge comprising a cartridge body which definessaid plurality of cavities and a plurality of inserts positioned withinsaid cavities.
 6. A co-extrusion apparatus as recited in claim 5,wherein at least one of said inserts comprises a pair of parallel railsspaced along a width direction, a web extending between said pair ofparallel rails and at least one indentation formed in said web.
 7. Aco-extrusion apparatus as recited in claim 1, wherein said combiningblock comprises a removable flow velocity profiler cartridge, said flowvelocity profiler cartridge comprising a cartridge body defining aplurality of cavities and a plurality of inserts received in saidplurality of cavities; at least one of said inserts comprising a pair ofparallel rails spaced along a width direction, a web extending betweensaid pair of parallel rails, said web having at least two indentationsforming at least two passageways through said flow velocity profilercartridge.
 8. A co-extrusion apparatus comprising a layer sequencer, atransitional aspect ratio block, and a flow velocity profiler cartridge,said layer sequencer comprising a plurality of channels; saidtransitional aspect ratio block comprising a plurality of passages whichcommunicate with said channels and which converge; said flow velocityprofiler cartridge defining a plurality of cavities which communicatewith said passages and which converge, said flow velocity profilercartridge comprising a plurality of inserts each positioned in one ofsaid plurality of cavities; at least one of said plurality of insertscomprising a pair of parallel rails spaced along a width direction, aweb extending between said pair of parallel rails and at least twoindentations formed in said web and forming at least two passagewaysthrough said flow velocity profiler cartridge.
 9. A co-extrusionapparatus as recited in claim 8, wherein said flow velocity profilercartridge comprises at least two inlets communicating with one of saidcavities such that each of said at least two passageways communicatewith one of said at least two inlets.
 10. A co-extrusion apparatus asrecited in claim 8, wherein each of said at least two indentations has arectangular cross-section.
 11. A co-extrusion apparatus as recited inclaim 8, wherein said flow velocity profiler cartridge comprises a pairof side caps enclosing side portions of said cartridge body.
 12. Alaminated plastic material comprising a plurality of layers, at leastone of said plurality of layers comprising a plurality of lanes, a firstof said lanes comprising a first polymer composition, a second of saidlanes comprising a second polymer composition, said second polymercomposition being different from said first polymer composition.
 13. Alaminated plastic material as recited in claim 12, wherein said firstlane is a first color and said second lane is a second color, saidsecond color being different from said first color.
 14. A laminatedplastic material as recited in claim 13, wherein said first and secondlanes are adjacent to each other and a feathered weld line is positionedbetween said first and second lanes.
 15. A laminated plastic material asrecited in claim 12, wherein said first and second lanes are adjacent toeach other and have different heat conduction properties.
 16. Alaminated plastic material as recited in claim 12, wherein said firstand second lanes are adjacent to each other and have differentmechanical properties.
 17. A laminated plastic material as recited inclaim 12, wherein said first and second lanes are adjacent to each otherand have different tear strengths.
 18. A laminated plastic material asrecited in claim 12, wherein at least one of said plurality of lanescomprises an extrudable adhesive.
 19. A laminated plastic material asrecited in claim 12, wherein said first and second lanes are adjacent toeach other and an adhesion of said first lane is lower than an adhesionof said second lane.
 20. A laminated plastic material as recited inclaim 12, wherein at least one of said plurality of lanes comprises afunctional coating.
 21. A laminated plastic material as recited in claim12, wherein at least one lane of said plurality of lanes comprisesacrylic resin.